1. Field of the invention:
The present invention relates generally to slide fasteners, and more particularly to a fluid-tight (airtight and watertight) slide fastener suitable for wet suits, life preservers, etc.
2. Description of the Prior Art:
U.S. Pat. No. 2,791,017, issued May 7, 1957 to F. Mulka, and U.S. Pat. No. 4,348,789, issued Sep. 14, 1982 to Brown, show a fluid-tight slide fastener of the type in which an inner longitudinal edge portion of each of opposed fluid-tight tapes is folded so as to extend around base portions of successive I-shaped coupling elements and in which successive C-shaped clamping strips surround, in clenched form, the folded edge portion over the base portion of the respective coupling element. The fluid-tight tape is relatively thick and is chiefly composed of rubber or synthetic resin having a certain degree of rigidness which is required for stable attachment of the coupling elements to the tape.
A problem with the known fluid-tight slide fastener is that smooth movement of a slider is difficult to achieve, partly because of such thick and rigid tape, and partly because the folded edge portion of the tape tends to restore its initial unfolded shape due to its own resilience.
Further, because of the rigidness of the tape, intimate contact between the opposed tapes at their contact portions contiguous to the respective folded edge portions can be impaired when lateral pulling forces are exerted on the tapes while the slide fastener is closed.